Perpetual Calendar Watches give the date, day, month and usually moon phases while automatically taking the number of days in the month, and the cycle of leap years, into account. Citizen Perpetual Calendar Watches will continue to show the correct date by adjusting to the variable number of days in the month and by taking the cycle of leap years into account. To accomplish this exploit, the movement draws on a "mechanical memory" of 1,461 days or four years. At BlueDial.com we carry several different styles of Citizen Perpetual Calendar Watches like the Citizen Calibre Watch collection, Eco-Drive Perpetual Calendar watches in Stainless steel, Titanium or strap watches and many more. When buying from an authorized Citizen dealer, watches are brand new, genuine, covered by 5 year warranty, with original manufacturers box and manual.